COLOR!

One colorblind person says he can't see any difference in color between a ripe orange and grass.  When he looks at the above arrangement of colors the grass colored cube (front, left, center) looks just like the ripe-orange colored cube (front, right, center).

This color vision is  "protanopic."  The retinas have no "red" sensitive cones.  Try to imagine what he sees when he looks at the above cube of cubes.

When you have it figured out, scroll down and see...
 
 
 
 
 
 
 
 
 
 
 
 
 

 
"Normal" color has:
 "Blue" sensitive cones
 "Green" sensitive cones
 "Red" sensitive cones 
Protanopic color has:
 "Blue" sensitive cones
"Green" sensitive cones
 No "red" sensitive cones
Protanopic color vision sees those three vertical planes of cubes as identical.  Arranging all the colors distinguishable to a protanope requires only two dimensions.  But add the "red" sensitive cone to his retina, and you would add one more dimension to the space he would  need to arrange all the colors that his vision would then distinguish.  Two dimensions would become three.

Question:

You probably recall that colors can be identified according to their "hue," "saturation," and "luminance," the Munsell parameters.  Hue distinguishes red from blue from chartreuse.  Saturation distinguishes pink from brilliant red.  Luminance distinguishes dark brick red from brilliant red.  In the "normal" view above you can see "luminance" as being the diagonal from far, upper right to near, lower left.  "Saturation" is distance outward from that diagonal line.  "Hue" is angular direction within the plane perpendicular to that line.  What has happened to those Munsell parameters, hue, saturation and luminance, in the protanopic arrangement?  Hint: Hue, saturation and luminance describe a three dimensional system, and protanopic color is two dimensional.
 

Note: We can only approximate showing a color "normal" person what a colorblind person sees.  Here protanopia is synthesized by simply removing the red phosphor from your computer screen's picture.  (Check it out with a strong magnifying glass.)  The following excellent Web sites look into this in greater detail:
 Web pages through colorblind eyes
Color Laboratory - HTML Writers Guild
The familiar colored-dot colorblindness tests